Containers such as PET bottles have shrink labels formed in cylindrical shapes attached thereon in order to display product names or the like and achieve decorative effects. Generally, such a cylindrical shrink label is formed by curling a label base material in a cylindrical shape and jointing overlapping opposite ends. Jointed ends are achieved by using, for example, solvent (solvent welding), adhesive, or the like.
It is necessary to peel a shrink label off a container to separate the label from the container in order to discard the labeled container to which the shrink label is attached. A common method for this separation is to form a tearing aid line such as a perforation with the label such that the label can be torn apart by using the aid (refer to, for example, Patent Document 1). There is also suggested another method, in which the jointed ends are formed with an adhesive which is soluble in an alkaline solution, whereby the jointed ends are peeled away from each other by immersing the labeled container into the alkaline solution (refer to, for example, Patent Document 2).